Make-before-break relays



y 1953 F. D. REYNOLDS 2,836,673

MAKE BEFORE-BREAK RELAYS Filed Oct. 28. 1954 Low REL ucma/c E ///6# Eu UCTANCE INVENTOR. FRANC/J 0 RYUOA 05 ATTOQ. ME Y5 United States PatentO MAKE-BEFORE-BREAK RELAYS Application October 28, 1954, Serial No. 465,204 Claims. Cl. 200-87 This invention relates to a novel, electromechanical relay device of a double-throw type having dual sets of contacts and so constituted that upon encrgization of the relay coil, the contacts of one set are engaged before the contacts of the second set are disengaged, or vice versa. Such a relay may properly be designated a make-beforebreak relay. The invention is herein illustratively described by reference to its presently preferred forms employing the principle of magnetically self-returning ball armature elements as disclosed and claimed in my copending application Serial No. 465,259, filed October 28, 1954. However, it will be recognized that certain modifications and changes therein with respect to details may be employed without departing from the inventive principles involved.

In certain electric circuit applications it is necessary or convenient to provide switching apparatus by which one circuit is closed (or opened) before a second circuit is opened (or closed); moreover, it is often desirable.

to accomplish such a change-over or reversal in circuit connections in a relatively short interval of time, and automatically, in response to a relay energizing (or deenergizing) change of voltage applied to the relay coil means. A general object of the present invention is the provision of a practicable and reliable electromechanical relay device accomplishing these results.

A related object is such a relay device of relatively simple and rugged construction, possessed of a long operating life expectancy and relative freedom from disturbance of its contacts positionally by shock, vibration or acceleration in any direction.

In its preferred form as herein disclosed such relay comprises a ferromagnetic core structure having two separately defined, relatively low-retentivity magnetic flux paths which are magnetizable by energization of relay coil means arranged to apply magnetizing force thereto simultaneously. Said flux paths have air gaps interposed therein each to receive a relay armature ball individual thereto,-and one such flux path has asociated therewith means delaying the generation of armatureball-attracting magnetic flux in such flux path relative to the generation of such magnetic fiux in the other flux path upon energization of the relay coil means. Assuming the armature balls occupy a normal switching position displaced from immediate proximity or contact with one of their respectively associated magnetic pole face surfaces, energization of the relay coil means will produce magnetic attraction of said armature balls toward such magnetic pole face surfacesin sequential order, with a predetermined delay taking place between such movements so as to permit one such ball to reach the actuated position before the second ball leaves the normal position. Permanent magnet means associated with the fer romagnetic core structure has one pole face disposed adjacent said air gaps to attract the balls into said normal positions in the absence of energization of said relay coil means. Preferably said pole face surfaces and the 7 2,836,673 Patented May 27, 1958 ICE 2 said permanent magnet pole are adapted as the electrical contacts of the relay and for such purpose are separately insulated from each other.

In accordance with one illustrated embodiment of the invention one of the separately defined magnetic flux paths of the ferromagnetic core structure is formed by means presenting a relatively high magnetic reluctance, whereas the other flux path presents a relatively low magnetic reluctance, whereby the build-up of magnetic flux in the first such path to the value necessary for armature ball attraction is slower than in the second such path, and the associated armature balls are therefore attracted sequentially into actuated position upon energization of the relay coil means.

In a second preferred embodiment of the invention the sequential attraction of the balls into actuated position is effected by providing a relatively low resistance in.

ductance element inductively linked substantially exclusively with the delayed-increase flux path and provided with a closed circuit connection permitting flow of induced current in said inductance element accompanying change of magnetic flux in such path, thereby to delay the build-up of magnetic flux in such path to actuating value relative to the build-up of ball-actuating flux in the other path.

An interesting aspect in the operation of such a relay device is that the conditions producing sequential attraction of the armature balls upon energization of therelay coil means likewise result, at least in certain embodiments, in reverse sequential movement of the balls into their normal positions under the impelling force of the permanent magnet upon deenergization of said coil means.

These and other features, objects and advantages of the invention will become more fully evident from the following description thereof by reference to the accompanying drawings.

Figure 1 is a simplified perspective view of the firstmentioned form of the novel relay device.

Figure 2 is a simplified perspective view of the secondmentioned form of such device.

Referring to Figure 1, one of the two separately defined magnetic flux paths is formed by the low-retentivity ferromagnetic core structure element 10, and the second such path by the similar element 12 disposed in side-byside relationship therewith. Preferably the two ferromagnetic elements 10 and 12 are of U shape, and are magnetically separated from each other by spacing them in parallel relationship a short distance apart. In the illustrated application of the device the core structure elements 10 and 12 are electrically interconnected by a conductor 14. For a purpose to be described, the element 10 comprises an element in a magnetic flux path of relatively high magnetic reluctance relative to that of the separately defined flux path of the element 12. This result may be achieved by employing ferromagnetic materials of different reluctances for the respective elements 10 and 12. However, such result is preferably accomplished by inserting air gaps 10a and 12a of differ ent lengths in the respective paths as mentioned below, the air gap 1011 being materially longer than the gap 12a.

The two separately defined magnetic flux paths mentioned above are completed through alow-retentivity ferromagnetic core structure element 16, theslower end of which extends into close proximity with, but is electrically insulated from the coplanar lower end faces of the elements 10 and 12 by reason of air gaps 10a and 121': respectively. The upper end of the element 16,-however, terminates in a plane located slightly below the lower edges of the planar upper end faces of the elements 10 and 12 so as to define equal ball-receiving air gaps therebetween which are serially interposed in the respective separately defined magnetic flux paths formed by the elements and 12. In the illustration the upper end faces of the elements 10 and 12 lie in a common plane which is substantially perpendicular to the upper end face of the element 16 so that the two air gaps are formed by mutually perpendicular pole faces. An electrically conductive ferromagnetic relay armature ball element 18 is received in the air gap identified with the core structure element 10 and a similar ball 20 is likewise received in the air gap identified with the core structure element 12 as illustrated. The core structure element 16 serves as the supporting core for a single relay coil 22 wound therearound and provided with energizing terminals 22a and 22b.

The relay device shown in Figure lfurther comprises permanent magnet means formed and arranged to set up permanent magnet flux in the two air gaps described above, and through the armature balls 18 and 20, such that the armature balls normally are magnetically held in normal positions out of physical contact with the upper pole faces of the core structure elements 10 and 12, as illustrated in Figure 1. Such permanent magnet means in the example comprises a pair of similar U-shaped permanent magnets 24 and 26 which for convenience of illustration may be assumed to possess the same physical shapes as the core structure elements 10 and 12 and occupy the same positions as the latter elements relative to the core structure element 16, but situated on the opposite side of the latter. The permanent magnets 24 and 26 have upper pole faces disposed adjacent the air gaps occupied by the balls 18 and 20 and on the side of such air gaps directly opposite from the upper pole faces of the elements 10 and 12. In effect, the core structure element 16 serves as a keeper for the permanent magnets 24 and 26. The armature balls 18 and 20 are normally held in physical contact with the upper pole face of the element 16 and the respective upper pole faces of the permanent magnets 24 and 26. The permanent magnets are interconnected by an electrical conductor 28.

The conductor 14 interconnecting the core structure elements 10 and 12 extends to a relay contact terminal 14 adapted for connection to any chosen electric circuit point. The connecting conductor 28 similarly extends to a second relay contact terminal 28. A third conductor, 30, is connected to the ferromagnetic core structure element 16 and extends to a third relay contact terminal 30. In the normal position of the relay armature balls 18 and 20, bridging between the upper face of element 16 and the upper pole faces of the respective permanent magnets 24 and 26, the terminals 28' and 30 are electrically interconnected by the armature balls. However, when energizing voltage is applied to the relay coil terminals 22a and 22b of a suflicient magnitude and with a polarity making the upper face of the core element 16 a magnetic pole of opposite polarity from that of the permanent magnet upper poles, magnetic flux will be established in the above described separately defined magnetic flux paths comprising the elements 10 and 12 to attract the balls 18 and 20 into actuated positions bridging directly between the upper face of the element 16 and the upper pole faces of the respective core structure elements 10 and 12. In this actuated position of the armature balls the terminals 14' and 30' are electrically interconnected. When energizing voltage is removed from the relay coil 22, the magnetic flux established previously in the elements 10 and 12 collapses because of the low magnetic retentivity of these elements and of the element 16, whereupon the substantially constant flux density of the permanent magnets 24 and 26 established in the ballreceiving air gaps again becomes sufficient to attract the armature balls back into their normal position illustrated in the figure.

' In accordance with an important feature .of the invention the twoarmature balls 18 and 20 do not simultaneously move from their normal position into actuated position upon energization of the relay coil 22. Instead, the ball 20, associated with the low-reluctance path comprising core structure element 12 is attracted into its actuated position before the ball 18 leaves its normal position.

This is due to the materially greater length of air gap 10a than that of air gap 120, as previously mentioned.

The theoretical explanation for the delay time interval between actuation of the armature balls 18 and 20 upon energization of the coil 22 is based on the observation that the finite electrical inductance of the coil 22 intro duces a certain delay or lag in the materialization of full magnetizing force applied to the two separate flux paths comprising the core structure elements 10 and 12, since current through the coil increases as an exponential function of time following application of energizing voltage to terminals 22a and 22b. Assuming the elements 10 and 12 are physically similar in form and in their magnetic coupling to magnetizing coil 22, the magnetizing force applied to the elements 10 and 12 is the same. Moreover, the rate of increase of magnetizing force applied to these elements is the same during the exponential rise of energizing current in the coil 22 immediately following application of energizing voltage to the coil terminals 22a and 22b. It is therefore apparent that the rate of flux density increase in the low-reluctance path of element 12 is materially greater than the rate of flux density increase in the path of element 10. Since the air gaps receiving the respective armature balls 18 and 20 are serially interposed in the separate flux paths comprised by elements 10 and 12, there will be a like relationship with respect to relative flux density increase in the two air gaps. Consequently, that flux density which is sufficient to attract the armature ball 20 from its normal position to its actuated position materializes at an earlier time during the exponential rise of magnetizing current in the coil 22 than does the corresponding flux density in the other air gap for attracting the armature ball 18 into its actuated position. By proper choice of design constants, that is by establishing a sufiicient difference between the magnetic reluctances of the flux paths respectively associated with elements 10 and 12, the armature ball 20 may be caused to move to its actuated position before the flux density in the air gap associated with the other armature ball 18 becomes suflicient to move the letter from its normal position toward actuated position, as desired.

When the coil 22 is deenergized the balls 18 and 20 are returned to their normal position by attraction of the flux of permanent magnets 24 and 26. Whereas the ball 20 was attracted to its actuated position before ball 18 upon coil energization, the ball 18 precedes the ball 20 in returning to its normal position upon coil deenergization. This reversal in the sequence of movement of the balls is attributable to the exponential decay of magnetizing force of coil 22 following removal of energizing voltage from such coil. The flux density in the high-reluctance magnetic path comprising element 10 therefore drops to a value below that sufiicient to hold ball 18 in actuated position materially before the flux density in the magnetic path comprising element 12 drops to a corresponding value.

It Will therefore be seen that the described makebefore-break action of the relay device illustrated in Figure 1 occurs both upon energization of relay coil 22 and also upon deenergization of that coil as a result of the differential magnetic reluctances of the two separately defined magnetic flux paths associated with the respective armature balls. It will be recognized that, relatively speaking, a complex sequence timing operation is accomplished by a highly simple and reliable apparatus. Moreover, in the preferred forms of the invention in which ball armature elements are utilized in accordance with basic principles of magnetically self-reequal length.

assay/s turning ball armature relays, as in the above-cited patent application, certain other advantages such as resistance to shock and vibration, etc, are inherently achieved in the novel structure.

In Figure 2 it may be assumed for convenience of explanation that parts bearing reference numerals similar to those applied in Figure l are similar to the parts which they identify in the former figure. Likewise for convenience the ferromagnetic core structure elements and 12 are given the same physical shape and disposition relatively as the core structure elements 10 and 12 in the preceding form, and all corresponding air gaps in their associated flux paths are made of substantially However, in this instance it is preferred that the flux paths associated with elements 10' and 12' possess equal magnetic reluctance, the sequential actuation of the armature balls between switching positions being accomplished by a different means than by differential reluctance. In this instance one of these armature elements, such as the element 10, has associated with it fiux-increase-delaying means in the form of a shorted-turn low resistance conductor 32, such as a copper ring, which constitutes an electrical inductance inductively linked with the element 10' and constituting a low resistance electrical path for flow of current induced therein when flux density changes in the member 10'. The core structure member 12 is not provided with a similar shorted-turn conductor. Consequently, when magnetizing force is applied to the core structure elements It? and 12 by energization of coil 22, there will be a certain counter-magnetizing force, produced by shorted-turn conductor 32, in the member 10' and no such force in the member 12'. As a result, magnetic flux density will build up in the air gap associated with armature ball 18 more slowly than in the air gap associated with ball 20, producing the desired sequential movement of the balls, as in the preceding form.

Upon deenergization of the relay coil 22 the collapse of magnetic flux in the core structure'element 10 will be retarded and prolonged by the inductive reaction of the shorted-turn conductor 32 relative to the accompanying collapse of magnetic flux in the core structure element 12. Consequently, the armature ball 18 is not only last to move from normal position to actuated position upon energization of coil 22, but such ball is also last to return to its normal position upon deenergization of the coil 22. Hence in this form no reversal of ball movement sequence takes place upon coil deenergization relative to that attending coil energization, as occurred in Figure 1.

One advantage of the form of the invention shown in Figure 2 over that shown in Figure 1 is that the equal steady state reluctances of the flux paths in Figure 2 tends to insure a somewhat greater vibration resistance than in the case of Figure 1, where differential reluctances are used. However the simplicity and design versality of the form shown in Figure 1 offers certain advantages where any of various suitable air gap lengths may be provided as by adjustable means to vary one pole face projection, hence the length of gap 10 relative to gap 12, or vice versa, and thereby permit varying the sequential timing or even reversing the ball actuating sequence.

In the case of Figure 2 a plurality of similar shortedturn conductors 32 may be used in order to increase the delay effect and, if desired, these may be selectively open-circuited by control switches interposed therein for varying the sequence timing.

These and other aspects of the invention, together with the various modifications and changes therein which are possible within the scope of the invention will be recognized by those skilled in the art.

I claim as my invention:

1. A relay device comprising electromagnet means ineluding a ferromagnetic core structure having ferromagnetic means forming two separately defined magnetic flux paths of relatively low magnetic retentivity each with a pair of mutually opposed magnetic pole face surfaces spaced apart relatively to form an air gap interposed in each such flux path, a pair of ferromagnetic relay armature balls movably received in the respective air gaps to permit movement of such balls between normal positions thereof displaced from immediate proximity with at least one of the associated gap-defining surfaces and relay-actuated position thereof magnetically bridging across their respective air gaps more directly between the associated pole face surfaces relatively than in said normal position, relay coil means arranged and electrically energizable to magnetize said core structure and thereby attract said armature balls into such relay-actuated position, permanent magnet means having mutually opposed magnetic pole face surfaces disposed respectively adjacent said air gaps and setting up magnetic flux in said air gaps to attract said relay armature balls into said normal positions thereof in the absence of magnetization of said ferromagnetic core structure, said magnetic core structure having therewith means relaying the increase of armature-ball-attracting magnetic flux in one of said flux paths relative to the increase of such magnetic flux in the other of said flux paths upon energization of said relay coil means, whereby one of said armature balls is moved into its relay actuated position before the other of said balls leaves its normal position, and at least two sets of electrical switch contact means for each of said armature balls, the respective sets being alternately engageable and disengageable by interpositional movement of said armature balls.

2. The relay device defined in claim 1, wherein mutually opposed magnetic pole face surfaces of the ferromagnetic structure comprise one of the sets of switch contact means, and mutually opposed magnetic pole face surfaces of the permanent magnet means comprise the other set of switch contact means, the relay armature balls electrically contacting the respective mutually opposed magnetic pole face surfaces in the positions of contact engagement of said armature balls operatively associated therewith.

3. The relay device defined in claim 1, wherein the flux-increase-delaying means comprises, in the ferromagnetic means forming the two separately defined magnetic flux paths feiromagnetic elements separated to form a relatively wide series air gap imparting a relatively high magneticreluctance to the delayed-increase flux path, and ferromagnetic elements formed and arranged to impart a relatively low magnetic reluctance to the other flux path, and the relay coil means is arranged to apply and remove magnetizing force to and from the ferromagnetic means and the two magnetic flux paths defined thereby substantially non-selectively of either of said flux paths.

4. The relay device defined in claim 1, wherein the flux-increase-delaying means comprises a relatively low resistance inductance element inductively linked selectively with said latter magnetic flux path and having a closed circuit connection permitting flow of induced current in said inductance element accompanying changes of magnetic flux in such path, thereby to produce countermagnetizing force opposing such changes, and the relay coil means is arranged to apply and remove magnetizing force to and from the ferromagnetic means and the two magnetic flux paths defined thereby substantially nonselectively of either of said flux paths.

5. A relay device comprising electromagnetic means including a ferromagnetic core structure having ferromagnetic means forming two separately defined magnetic flux paths of relatively low magnetic retentivity each with a pair of mutually opposed magnetic pole face surfaces spaced apart relatively to form an air gap interposed in each such flux path, a pair of ferromagnetic relay armaaseaevs ture elements movably received in the respective air gaps to permit movement of such armature elements between normal position thereof displaced from immediate proximity with at least one of the associated gap-defining surfaces and relay-actuated position thereof magnetically bridging across their respective air gaps more directly between the associated pole face surfaces relatively than in said normal position, relay coil means arranged and electrically energizable to magnetize said core structure and thereby attract said armature elements into such relay-actuated position, permanent magnet means having mutually opposed magnetic pole face surfaces disposed respectively adjacent said air gaps and setting up magnetic flux in said air gaps to attract said relay armature elements into said normal positions thereof in the absence of magnetization of said ferromagnetic core structure, said magnetic core structure having therewith means delaying the increase of armature-ball-attracting magnetic flux in one of said flux paths relative to the increase of such magnetic flux in the other of said flux paths upon energization of said relay coil means, whereby one of said armature elements is moved into its relay-actuated position before the other of said armature elements leaves its normal position, and at least two sets of electrical switch contact means for each of said armature elements, the respective sets being alternately engageable and disengageable by interpositional movement of said armature elements.

6. The relay device defined in claim 5, wherein the fluX-increase-delaying means comprises, in the ferromagnetic means forming the two separately defined magnetic flux paths, elements respectively imparting a high magnetic reluctance to the delayed-increase flux path relative to the magnetic reluctance imparted thereby to the other flux path, and the. relay coil means is arranged to apply and remove magnetizing force to and from the ferromagnetic means and the two magnetic flux paths defined thereby substantially non-selectively of either of said flux paths.

7. The relay device defined in claim 5, wherein the flux-increase-delay means comprises a relatively low resistance inductance element inductively linked selectively with said latter magnetic fiux path and having a closed circuit connection permitting flow of induced current in said inductance element accompanying changes of magnetic flux in such path, thereby to produce countermagnetizing force opposing such changes, and the relay coil means is arranged to apply and remove magnetizing force to and from the ferromagnetic means and two magnetic flux paths defined thereby substantially non-selectively of either of said flux paths.

8. A relay device comprising electromagnet means inciuding a ferromagnetic core structure having ferro-rnagnetic means forming two separately defined magnetic flux paths of relatively low magnetic retentivity each with pair of mutually opposed magnetic pole face surfaces spaced apart relatively to form an air gap inter posed in each such flux path, the mutually opposed pole face surfaces in each such pair being disposed substantially transversely to each other, and sai ferromagnetic means having included therein at least one ferromagnetic element interposed serially in said magnetic flux paths and having an end face comprising one of the two pole face surfaces in each of said pairs of surfaces, said ferromagnetic element pole face surface being electrically insulated from the respectively opposing magnetic pole face surfaces, 21 pair of ferromagnetic relay armature balls movably received in the respective air gaps to permit movement of such armature balls between normal the positions thereof displaced from immediate proximity with the last mentioned pole face surfaces, and relayactuated position thereof magnetically and electrically bridging directly between their respective pole face surfaces to establish electrical contact thcrebetween, relay coil means arranged and electrically energizable to magnetize said core structure and thereby attract said armature balls into such relay-actuated position, permanent magnet means having one pole disposed adjacent said ferromagnetic element pole face surface in generally transverse relationship therewith and spaced from said second-mentioned pole face surfaces in the direction of displacement of said armature bails toward the normal positions thereof, said permanent magnet means having an opposite pole disposed adjacent said ferromagnetic element to pass permanent magnet flux through said element and through said air gaps to attract said relay armature balls into the respective normal positions thereof in the absence of energization of said relay coil means, the first-mentioned magnetic pole of said permanent magnet means having electrically conductive pole face surfaces contacted by said armature balls in the normal positions thereof and being otherwise electrically insuiated from said ferromagnetic core structure, said magnetic core structurehaving therewith means delaying the increase of armature-ball attracting magnetic flux in one of said flux paths relative to the increase of such magnetic flux in the other of said flux paths upon energization of said relay coil means, whereby one of said armature balls is moved into its relay-actuated position before the other of said armature balls leaves'its normal position, and electrical connections to the ferromagnetic core structure pole face surfaces and to the first-mentioned permanent magnet means pole face surface adapting such surfaces as separate relay contacts for connection in electrical circuits.

9. The relay device defined in claim 8, wherein the fluX-increase-delaying means comprises, in the ferro magnetic means forming the two separately defined magnetic flux paths, elements respectively imparting a high magnetic reluctance to the delayedincrease flux path relative to the reluctance imparted thereby to t.e oti er flux path, and the relay coil means is arranged to apply and remove magnetizing force to and from the ferromagnetic means and the two magnetic flux paths defined thereby substantially non-selectively of either of said flux paths. 7

10. The relay device defined in claim 8, wherein the fiux-increase-delaying means comprises a relatively low resistance inductance element inductively linked selectively with said latter magnetic flux path and having a closed circuit connection permitting flow of induced current in said inductance element accompanying changes of magnetic flux in such path, thereby to produce countermagnetizing force opposing such changes, and the relay coil means is arranged to apply and remove magnetizing force to and from the ferromagnetic means and the tvo magnetic flux paths defined thereby substantially nonselectively of either of said flux paths.

References Cited in the file of this patent UNITED STATES PATENTS 684,378 Potter Oct. 8, 1901 685,549 Wurts Oct. 29, 1901 2,111,550 Armstrong Mar. 22, 1938 2,238,913 Miller Apr. 22,. 1941 2,253,856 Harrison Aug. 26, 1941 2,732,454 Buckingham Jan. 24, 1956 2,732,458 Buckingham Jan. 24, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,836,673 May 27, 1958 Francis D a Reynolds It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 23, for "relaying" read me delaying a Signed and sealed this 4th day of November 1958.,

XSEAL) ttest:

KARL H, AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,836,673 May 27, 1958 Francis Do Reynolds It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 23, for "relaying" read delaying Signed and sealed this 4th day of November 1958,

XSEAL) ttest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

